We plan to study the physiologic mechanisms involved in initiation and recovery from apneic spells. Special emphasis is given for apnea associated with upper airway obstruction (obstructive and mixed apnea). First, we will study mechanical and neuro-muscular factors relevant to pharyngeal airway maintenance in anestetized living and in dead rabbits. These studies will include electromyography of the genioglossus, sternohyoid, sternothyroid and genoihyoid muscles. Reflex regulation of these muscles will be studied by denervation to eliminate afferent nerve supply. Second, in young infants with Pierre Robin syndrome (micrognathia, glossoptosis and obstructive apnea) we will study maturation of reflexes regulating the genioglossus muscle and neck extensor muscles. We will examine the possible role of these muscles in normal airway maintenance and in recovery from obstructive apnea. Studies will be conducted during rapid eye movement sleep and quiet sleep. Electromyography of airway muscles and diaphragm will be performed. Determinations of airway pressures and airway resistance will be made. Finally, in these infants and in preterm infants with mixed and obstructive apnea, we will examine the muscular mechanism of the airway obstruction during apnea and the therapeutic effect of administered vestibular and tactile stimuli. Various respiratory reflexes which could account for spontaneous recovery from airway obstruction will be evaluated. These studies are viewed as relevant to the maturation and development of respiratory control in man and to the clinical syndromes of Pierre Robin syndrome, apnea of prematurity, sleep obstructive apnea and Sudden Infant Death Syndrome.